The present invention relates to a structure of a bottom bracket and more particularly to an improved structure of a bottom bracket having tapered engaging peripheral surfaces formed between a cap and a tube thereof.
A conventional bottom bracket includes a housing, a tube disposed in the housing, an axle rotatably engaged in the tube with bearings disposed therebetween and a cap threadedly engaged to an end of the housing. The engagement between the cap and the axle will loosen due to the vibration when riding on a rugged road.
The most relevant art of which applicant is aware is his prior U.S. Pat. No. 5,181,437 to Chi, entitled "HUB 0F A BICYCLE", filed Jul. 13, 1992. Generally, the tube 30 is rotatably engaged to the shell 20, and has a cone 31 formed integrally on the outer peripheral portion of one end, the cone 31 including a tapered surface 32 formed in the outer peripheral portion thereof for engagement with the tapered surface 22 of the hub shell 20. The Cap 35 includes an inner thread 36 formed therein for threaded engagement with the outer thread 33 of the tube 30 and includes a tapered surface 37 formed in the outer peripheral portion thereof for engagement with the tapered surface 21 of the hub shell 20. There could be some gap existing between the tapered surfaces 32, 22 if some manufacturing errors have occurred in manufacturing the thread portions 33, 36, or if the assembling operation between the cap and the tube is not precise enough. Moreover, the arrangement having no cap disposed in the end opposite to cap 35 will lead to serious damage of the bearings received in the tube by entry of grit, dust, water etc.
The present invention intends to provide an improved structure of a bottom bracket to mitigate and/or obviate the above mentioned problems.